I must be a cow

Danny Boy said
As an aside, may be urban legend..
I heard that skim milk was once a by product and difficult to dispose of in the sewers as it would bubble/backup

Also heard that kerosene(diesel?) was also a biproduct. Now hard to find and expensive

It was the other way around...gasoline was the unwanted byproduct. Nobody wanted it as all they wanted was the kerosene and fuel oil. Gasoline was considered too volatile to be useful.